In general, spine related diseases, can be treated by indirect methods utilizing physical therapy and direct methods by correcting and fixing the spine by installing a separate fixation device in the damaged part of the spine. That is, while minor spinal diseases can be treated by physical therapy, serious diseases in cervical, thoracic, lumbar and sacral regions and intervertebral discs that make up the spine are treated by using a separate spinal fixation device.
A spinal fixation device commonly used in surgery includes a pedicle (sacrum) screw which is inserted into the pedicle or sacrum of the vertebra at a predetermined angle and depth, a spinal rod disposed on one side of the spinal part, and a fixing cap or a fastener to fasten the spinal rod and the pedicle screw together, in order to correct the damaged part of the spine to normal condition and fix it without movement. To treat the damaged part of the spine, the pedicle screw is inserted and fixed into the pedicle or sacrum of the vertebra in optimum direction and position first, and then the spinal part is corrected to normal condition using the spinal rod, and the spinal rod and the fixing screw are fixed using the fixing cap or the fastener, and thus treatment is completed.
However, degeneration of the previous surgical site up and below requires re-surgery that is called symptomatic adjacent segment degeneration, and in such a case, it is necessary to connect an existing screw and a new screw, and since this process involves making an incision in the previous surgical site to replace the rod, it causes mental, physical and financial burdens for the patient. Recently, to solve this problem, a method (Korean Patent Application No. 10-2012-7000779) is proposed in which a connector is fitted to an existing rod and a new rod is connected to another hole of the connector; however, this method requires accurate 11-shaped arrangement of the rods due to the feature of the connector, that places limitations on the positional relationship between the rods, and since it is necessary to sufficiently remove the surrounding area of the rod, it causes problems where the surgery is still not easy and many burdens are imposed on the patient.